1. Field of the Invention
The invention relates to a field bus arrangement comprising at least one field bus station adapted to be connected with a serial field bus and at least one load adapted to be controlled by way of a control output of the field bus station.
2. Description of the Prior Art
Field bus arrangements for the serial control of spatially separate loads and load arrangements via field bus stations from a central control unit have been proposed in many different designs and variations, see for example the German patent publication 4,226,682 A, the German patent publication 3,631,477 A, the British patent publication 2,123,589 B or the periodical Elektronik 11, 3.6.1983, "Das lokale SP-Netzwerk", pages 73 through 78. In th case of the known arrangements in each case several field bus stations (or field bus nodes) are connected with the field bus consisting of customarily two or three lines by way of a central control unit. The same transmits serial data telegrams along the field bus and communicates via an address comprised in the data telegram with the field bus station assigned in the data telegram. In accordance with the control commands received such field bus station then directly controls, by way of control outputs, one or more of the connected loads. By way of the field bus there is then a transmission both of the control signals and also of the necessary electrical power for the supply of the field bus stations and for direct control of the loads. This means that there is on the one hand the need for elaborate and expensive field bus stations and on the other hand there is the danger of spurious activation of loads owing to defective data telegrams in the field bus, something which is unacceptable for many applications having high requirements as regards safety standards.